Revert "Fix hstore parse number conversion"

This reverts commit 48e04c4de24462ec761852d0efd8949fd57579b4.

Unfortunately, after reviewing this with @fixe, we concluded that it is bad practice to parse all numbers as float, particularly if you're storing numbers with precision larger than the maximum supported.

Since `HSTORE` does not allow us to strongly-type a value (unlike `JSON`), it is not possible to reliably determine the data type that was originally stored. It is therefore our opinion that Sequelize should not assume that any value can be a number.

This issue will be somewhat mitigated when Postgres 9.4 arrives which will bring high-performance `JSON` support (which inherently strongly-types numbers).